Nanoshaped CuO/CeO2 Materials: Effect of the Exposed Ceria Surfaces on Catalytic Activity in N2O Decomposition Reaction

This study reports a thorough investigation of nanosized CuO/CeO2 materials as an efficient catalyst for decomposition of N2O, which is strong greenhouse gas largely produced by chemical industry. Effect of terminating CeO2 crystalline planes ({100}, {110}, and {111}) on the behavior of CuO dispersed over CeO2 nanocubes, nanorods and polyhedral crystallites was examined in detail by using a variety of catalyst characterization techniques. The 4 wt % Cu was found as the most advantageous metal loading, whereas higher Cu content resulted in lower dispersion and formation of significantly less active, segregated bulk CuO phase. It was discovered that CuO/CeO2 solids should enable both excessive oxygen mobility on the catalyst surface as well as formation of highly reducible Cu defect sites, in order to ensure high intrinsic activity. Detailed studies further revealed that CeO2 morphology needs to be tailored to expose {100} and {110} high-energy surface planes, as present in CeO2 nanorods. Oxygen mobility and regeneration of active Cu phase on these surface planes is easier, which in turn facilitates higher catalytic activity through the recombination of surface oxygen atoms and desorption as molecular oxygen that replenishes active sites for subsequent catalytic cycles. As a consequence, CuO supported on CeO2 nanorods demonstrated lower activation energy (87 kJ/mol) in N2O decomposition reaction compared to catalysts based on CeO2 nanocubes (102 kJ/mol) or polyhedral CeO2 (92 kJ/mol).